Field of the Invention
The present invention relates to a converter lens device for an optical system having a focal length longer than a focal length of an optical system of a master lens device, and to a photographing system including such a converter lens device.
Description of the Related Art
A converter lens is known as an optical system for changing the focal length of a master lens. In application, the converter lens is attached to an object side of the master lens or an image side of the master lens. The converter lens attached to the image side of the master lens is called a rear converter lens.
A converter lens device including a rear converter lens includes two mounts. One of the mounts is a mount associated with a mount of a master lens device, and the other mount is a mount associated with a mount of a camera body.
In application of the converter lens device, the converter lens device is disposed between the master lens device and the camera body such that each of the two mounts is interposed between the converter lens device and the master lens device or the camera body. In this manner, the focal length of the master lens can be changed. A rear converter lens for increasing the focal length of a master lens is called a rear teleconverter lens.
The focal length of the master lens can be increased. For this reason, rear teleconverter lenses are used for users of single-lens reflex cameras with interchangeable lenses, especially users who perform telephotographing.
A camera system not using a quick return mirror, that is, a camera system whose size and thickness are reduced by reducing a flange focal distance, has been known. For such a camera system, a rear teleconverter lens is also demanded.